1. Field of the Invention
This invention relates to apparatus and methods for shrinking heat shrinkable film wrapped about a product.
2. Description of the Related Art
It is common to wrap products in a plastic heat shrinkable film and then to shrink the film so as to both protect the product and to display it in a commercially attractive manner. In the initial process of wrapping, the film is typically sealed along the bottom of the product on a line parallel to the conveyor path and then sealed before and behind the product on a pair of lines perpendicular to the conveyor path. The result of this process is generally a product loosely wrapped in a sealed plastic film pouch. To make this film wrap commercially attractive, heat is applied to the film to cause it to shrink and achieve intimate wrinkle-free contact with the product contents.
The process described above is particularly common in food packaging, and especially in poultry packaging. An improved process for the shrinking of heat-shrinkable films is described in U.S. Pat. No. 5,193,290 for an APPARATUS AND METHOD FOR SEQUENTIAL SHRINKING OF PACKAGING FILM, the teaching of which is incorporated herein by reference.
The United States Department of Agriculture has recently issued a directive requiring that each retail package containing a meat product must be labeled with safe handling instructions concerning storage, preparation, cooking and preservation of leftovers. This new directive requires that the instructions be readable and that the direction of print on the top of the package be the same as on the bottom of the package. In response to this directive and for reasons of appearance and economy, it has been found desirable to print the information needed directly on the film in which the product is being wrapped rather than on a separate label. In the case of a tray in which poultry parts are packaged, the four lateral sides of the film wrapped around the tray are not suitable for such print because of the small size of the side area and the fact that the sides are typically tapered inwardly, which places the side areas generally out of view. The acceptable areas for printing an instruction panel are thus the bottom and the top surfaces of the film-wrapped package. Since a longitudinal seam is typically formed along the center of the tray bottom surface, the printing area on the film bottom is thus divided into two portions.
Whereas the apparatus and method of the U.S. Pat. No. '290 patent cited above has led to substantial improvement in the overall appearance of the top and side surfaces of the film on the poultry package, there was heretofore no concern about the appearance of the bottom surface or its suitability for carrying printed instructions. Upon attempting to shrink film printed in areas which correspond to the top and bottom of the tray containing poultry, it has been discovered that the bottom surface of the tray film tends to be excessively wrinkled, shrinks a considerable amount, and somewhat discolors due to the application of high heat. These combined effects cause the segments of print on the film package bottom to be unacceptable in appearance and unreadable.
It is therefore an object of this invention to provide an apparatus and method which enables heat shrink film wrapped around a package to be substantially wrinkle free on the top and the bottom surfaces after being shrunk so that information printed thereon is readable.
It is another object of this invention to provide an apparatus and method to shrink film wrapped around a package while preventing heat-caused discoloration of the film.
Other objects and advantages will be more fully apparent from the following disclosure and appended claims.